Question: How do Cepheids allow astronomers to measure intergalactic distances?ġ. Henrietta Leavitt’s work onĬepheids provided the key to solving this problem. It is only possible to use a star’s apparentīrightness to determine its distance if you know the star’s luminosity. It is a large, luminous star, or because it is very close. Or absolute brightness, and its distance from the observer. Introduction: Two factors determine how bright a star appears to an observer: its luminosity, On the STARS tab, check that Region A: NGCĢ24 (Andromeda Galaxy) is selected. The more a star pulses the dimmer the star is. Because both stars are in the same galaxy, they are about the same distance from Earth.īased on what you see, how is the brightness of the star related to how quickly it pulses? Which star takes longer to pulse? Star A-091 takes longer to pulse than the others.Ģ. Which star reaches a greater apparent brightness? Star A-091 has a greater apparentī. Is the yellow star, and A-171 is the white star.Ī. Locate the two Cepheid variables, the stars that change in brightness over time. Look at the image of theĪndromeda Galaxy, a galaxy relatively close to our own Milky Way galaxy.ġ. In the Big Bang Theory – Hubble’s Law Gizmo, select Region A. Other galaxies and eventually helped to support the Bigīang theory of the origin of the universe. Herĭiscoveries led to a method of measuring distances to Stars change from bright to dim to bright again. Studied a class of stars called Cepheid variables. In 1912, an astronomer named Henrietta Swan Leavitt If I know the light source is smaller, then the bicycle is closer than it is shown. What can you conclude about the distance of the motorcycle and bicycle? Suppose the dim-looking headlight on the right is actually a small light on the front of aīicycle. If the headlights are equally bright, which motorcycle is closer? The one on the left sideĮxplain: If it is brighter than that means its going to be closer because the light particles are travelingĢ. The headlight on your left appears brighter than the one on your right.ġ. Standing by the side of a lonely highway at night, you see two motorcycle headlights, one inĮach direction. Prior Knowledge Questions (Do these BEFORE using the Gizmo.) Megaparsec, period, redshift, spectrograph hift, Cepheid variable, Doppler shift, Hubble constant, Hubble’s law, luminosity, Vocabulary: absolute brightness, absorption spectrum, apparent brightness, Big Bang theory,īlues. Student Exploration: Big Bang Theory – Hubble’s Law
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